The present invention relates to a method as defined in the preamble of claim 1 for conveying material by applying a pressure difference in a conveying conduit, in which method the material is fed into the conveying conduit and in the conveying conduit further into a separating device, where the material being conveyed is separated from the conveying air, in which method a negative pressure is created in the conveying conduit by means of an ejector apparatus, whose suction side is connected to the separating device, said ejector apparatus being operated using an operating medium, which consists of a liquid mist, especially an aqueous liquid mist, said medium being sprayed through at least one spraying nozzle into an ejector tube directed into a separating element.
The invention also relates to an apparatus as defined in the preamble of claim 10 for conveying material, preferably bulk material in food industry, in particular slaughtering offal and food waste, or working residual in engineering industry, by the application of a pressure difference in a conveying conduit, said apparatus comprising a material conveying conduit, a separating device and means for creating a negative pressure in the conveying conduit by using an ejector apparatus whose suction side is connected to the separating device, said ejector apparatus being operated using an operating medium and comprising at least one nozzle for spraying a liquid mist and for using the liquid mist as the operating medium of the ejector and means for supplying a liquid to the nozzle, and which apparatus comprises at least one ejector nozzle arranged in or near an ejector tube, said ejector tube being directed towards the separating element and extending into the separating element.
There are prior-art material-conveying systems operated by utilizing a pressure difference, designed especially for conveying food products, such as meat products. A system of this type is disclosed in specification WO 88/01597 A. Numerous corresponding solutions exist. There are also apparatus used in conjunction with e.g. ships' galleys, where material is conveyed in a corresponding manner, typically from several places to one or more containers or for further processing. Such apparatus are also used for conveying foodstuffs and waste in various establishments. Typically, they produce a negative pressure by using a vacuum system in which a negative pressure is created in a conveying conduit by means of vacuum generators, such as an ejector apparatus. In an ejector apparatus, a suction is typically created in a conveying conduit by an ejector in which a pneumatic apparatus is used to spray pressurized air into a nozzle, which again creates a negative pressure in the conveying conduit. The conveying conduit is typically provided with at least one valve element, and the amount of replacement air entering the conduit is regulated by opening and closing the valve element. In prior-art solutions, pneumatic air is supplied to the ejector apparatus at a constant pressure. This therefore always involves the same energy consumption regardless of the actual need for pneumatic air. In possible blockage situations in the conveying conduit system, prior-art solutions have a limited applicability for clearing blockages or they require separate apparatus for this purpose. Further, current solutions have limitations regarding adaptation to conveying materials involving different requirements. Moreover, in prior-art solutions the material to be conveyed may cause problems of smell and/or particles in the blast air of the vacuum apparatus, such as an ejector apparatus. The use of conventional vacuum pumps in conjunction with or in the environment of explosible materials is very restricted or even dangerous. Also, in some prior-art solutions a liquid mist is used in conjunction with such material conveying systems. This type of background of the method and apparatus of the invention is also described e.g. in specification WO 2005/085105 and in specification WO 2005/085104. It is an objective of the invention to further develop the systems disclosed in these specifications.
The object of the present invention is to achieve a completely new type of solution to avoid the drawbacks of prior-art solutions. The object of the invention is to create a solution that will make it possible to produce a more efficient suction by an ejector apparatus in general and in particular during blockages of the conduit system used to convey material. A second specific object of the invention is to create a solution in which, on the other hand, a good yield can be produced by the ejector apparatus and the generation of negative pressure can be enhanced according to need. A further object of the invention is to create an ejector apparatus that can be utilized as a vacuum generation unit in many types of applications using negative pressure. Yet another object is to create a vacuum generation unit that will be applicable for use in conjunction with explosible or inflammable materials or environments. An additional object of the invention is to create a system that will make it possible to avoid the possible disadvantages of smell and/or particles in prior-art solutions. Yet another object is to create an ejector solution that will reduce the energy requirement.